The present invention relates generally to an information recording/reproducing system for recording information in a three-dimensional optical recording medium and for reproducing information recorded in the medium. More specifically, the invention relates to an information recording/reproducing system for recording information in three-dimensional directions in an optical recording medium wherein digital data are recordable in three-dimensional directions, and for reproducing information recorded in the optical recording medium while precisely positioning recording and reproducing light beams in depth directions.
In recent years, the enhancement of density of optical recording media, such as optical disks, rapidly proceeds in information processing systems, such as computers. As such density-enhanced optical recording media, optical disks having a plurality of recording layers in depth directions have been studied.
In such optical recording disks having a plurality of recording layers, if a system for reading information included in reflected light beams, which are reflected on the respective layers, using the reflectance of the respective recording layers is adopted, the reflectance of the respective recording layers decreases as the increase of the number of the layers in accordance with the relationship between transmission and reflection, so that the signal strength decreases.
Against such a technique using reflected light beams, an optical head system adopting a system for recording transmitted light beams passing through a multilayered phase recording medium without using reflection on recording layers is disclosed in, e.g., Japanese Patent Laid Open No. 10-3684.
FIG. 1. shows a conventional information reproducing system for reading the transmittance of a multilayered phase recording medium. In this figure, light beams emitted from light irradiation means 1, such as a semiconductor laser, are collimated by a collimator lens 2, and part of the light beams pass through a beam splitter 3, such as a half mirror, to enter an objective lens 4 to be condensed in a phase type three-dimensional optical disk 5. Then, the light beams passing through the three-dimensional optical disk 5 are reflected on the reverse surface of the optical disk 5 to enter the objective lens 4 again as reflected light beams, and part of the reflected light beams are reflected by the beam splitter 3 to be detected by a photo detector 6.
As shown in FIG. 1, in the conventional reproducing system for the three-dimensional optical recording medium, it is required to further provide a phase/intensity modulating plate 7 to recondense light beams, which pass through the plate 7, on a pinhole 9 by means of a recondenser lens 8 to irradiate the photo detector 6 with laser beams passing through the pinhole 9.
As described above, the conventional reproducing system for the phase type three-dimensional recording medium requires additional constructions, such as the phase/intensity modulating plate, so that there are problems in that it is difficult to commonly use optical recording/reproducing systems, which have been widely used until now, and it is difficult to miniaturize the whole system.
In addition, the above described conventional information reproducing system for the three-dimensional recording medium does not take measures to cope with the adjustment of the focus of recording or reproducing light beams in depth directions. Therefore, when information is recorded on the three-dimensional optical recording medium or when information is read from the three-dimensional recording medium, it is difficult to adjust the focus of recording or reproducing light beams in depth directions, so that there is a problem in that it is not possible to obtain satisfied recording precision and reproducing precision.
Moreover, when data are recorded/reproduced in/from a plurality of layers having different depths of the above described three-dimensional optical recording medium, the distance between the objective lens and the recording medium must be adjusted for each of the different depths, so that there is a problem in that the time required for this adjustment prevents the accelerating of the recording/reproducing of data as the whole system.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a compact information recording/reproducing system capable of rapidly writing and reading data in/from a three-dimensional optical recording medium while positioning the three-dimensional optical recording medium in depth directions by utilizing an optical recording/reproducing system which has been used until now.
In order to accomplish the aforementioned and other objects, according to a first aspect of the present invention, there is provided a recording system for recording information in a three-dimensional optical recording medium wherein information is recordable at three-dimensional optional positions and wherein position reference regions having optical characteristics different from those of recordable regions are previously provided at predetermined positions, the recording system comprising: a light source configured to irradiate the vicinity of each of the position reference regions of the three-dimensional optical recording medium with a condensed light beam; a detector configured to detect the intensity of the light beam passing through the three-dimensional optical recording medium; a moving mechanism configured to move the condensed position of the light beam, which is emitted from the light source, with respect to the three-dimensional optical recording medium on the basis of the detected result obtained by the detector; and a light intensity adjuster configured to change the intensity of the light beam, which is emitted from the light source to the three-dimensional optical recording medium, to a recordable intensity.
According to a second aspect of the present invention, there is provided a reproducing system for reproducing recorded information from a three-dimensional optical recording medium capable of recording information at three-dimensional optional positions, the reproducing system comprising: a light source configured to irradiate the three-dimensional optical recording medium; a condenser configured to condense the light beam, which is emitted from the light source, in the vicinity of each of position reference regions which are previously provided at predetermined positions of the three-dimensional optical recording medium and which have optical characteristics different from those of recordable regions, or in the vicinity of each of recording regions for information recorded in the recordable regions; a detector configured to detect the intensity of the reference light beam passing through the three-dimensional optical recording medium; a moving mechanism configured to move the condensed position of the light beam, which is emitted from the light source, with respect to the three-dimensional optical recording medium on the basis of the detected result obtained by the detector; and a reproducing device configured to reproduce information by detecting the intensity of transmitted light of a reproducing light beam emitted from the light source to the three-dimensional optical recording medium.
According to a third aspect of the present invention, there is provided a recording system for recording information in a three-dimensional optical recording medium wherein information is recordable at three-dimensional optional positions and wherein position reference regions having optical characteristics different from those of recordable regions are previously provided at predetermined positions, the recording system comprising: a light source configured to irradiate the three-dimensional optical recording medium with light beams of a plurality of patterns having different wavelengths containing at least one of a positioning reference light beam having a first wavelength, an information recording light beam having an intensity sufficient to record information, and an information record confirming light beam having a second wavelength; a condenser configured to condense the reference light beam having the first wavelength emitted from the light source, in the vicinity of each of the position reference regions; and a position detector configured to detect the reference light beam passing through the three-dimensional optical recording medium to detect each of the optional positions of the three-dimensional optical recording medium, wherein the light source emits the recording light beam having the intensity sufficient to record information, on the basis of the detected position of the reference light beam detected by the position detector, and the condenser condenses the recording light beam at each of the optional positions of the three-dimensional optical recording medium.
According to a fourth aspect of the present invention, there is provided a reproducing system for reproducing recorded information from a three-dimensional optical recording medium capable of recording information at three-dimensional optional positions, the reproducing system comprising: a light source configured to irradiate the three-dimensional optical recording medium with light beams of a plurality of patterns having different wavelengths containing at least one of a positioning reference light beam having a first wavelength, and an information reproducing light beam having a second wavelength and an intensity sufficient to reproduce information; a condenser configured to condense the reference light beam having the first wavelength emitted from the light source, in the vicinity of each of the position reference regions which are previously provided at predetermined positions of the three-dimensional optical recording medium and which have optical characteristics different from those of recordable regions, or in the vicinity of each of recording regions for information recorded in the recordable regions; and a position detector configured to detect the reference light beam passing through the three-dimensional optical recording medium to detect each of the optional positions of the three-dimensional optical recording medium, wherein the light source emits the reproducing light beam having the second wavelength, on the basis of the detected position of the reference light beam detected by the position detector, and the condenser condenses the reproducing light beam at each of the optional positions of the three-dimensional optical recording medium.